Piezoelectric buzzers may be used to provide audible alerts in personal alert safety systems. Such buzzers typically use a small, thin sheet of material that can be vibrated by a piezoelectric material powered by an electric current to produce a loud buzzing sound. These buzzers are used, for example, by firefighters who wear the buzzers on their protective gear when entering a fire. When the firefighter is in trouble, such as when the firefighter is knocked to the ground, the buzzer will automatically emit a loud sound enabling others to locate and rescue the firefighter.
In emergency situations however, a firefighter and his equipment may be exposed to temperatures ranging from freezing to more than 250° C. Since the output of the buzzer may vary significantly over that temperature range, high temperature buzzers that are optimized for use at standard room temperatures may have their output significantly reduced in high- or low-temperature situations as the sound chamber is detuned relative to the diaphragm resonance.
A need therefore exists for an improved piezoelectric buzzer that provides a relatively consistent output signal strength over a broad temperature range. The present invention addresses that need.